linux-kernel - Re: [PATCH v3 02/11] cxl/region: Store HPA range in struct cxl

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Message-ID: <090fd415-42e4-481f-8c77-0b3f2e9f3f63@intel.com>
Date: Mon, 15 Sep 2025 09:24:09 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Robert Richter <rrichter@....com>
Cc: Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Davidlohr Bueso <dave@...olabs.net>, linux-cxl@...r.kernel.org,
 linux-kernel@...r.kernel.org, Gregory Price <gourry@...rry.net>,
 "Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>,
 Terry Bowman <terry.bowman@....com>, Joshua Hahn <joshua.hahnjy@...il.com>
Subject: Re: [PATCH v3 02/11] cxl/region: Store HPA range in struct cxl_region



On 9/15/25 12:19 AM, Robert Richter wrote:
> On 12.09.25 10:17:14, Dave Jiang wrote:
>>
>>
>> On 9/12/25 7:45 AM, Robert Richter wrote:
>>> Each region has a known host physical address (HPA) range it is
>>> assigned to. Endpoint decoders assigned to a region share the same HPA
>>> range. The region's address range is the system's physical address
>>> (SPA) range.
>>>
>>> Endpoint decoders in systems that need address translation use HPAs
>>> which are not SPAs. To make the SPA range accessible to the endpoint
>>> decoders, store and track the region's SPA range in struct cxl_region.
>>> Introduce the @hpa_range member to the struct. Now, the SPA range of
>>> an endpoint decoder can be determined based on its assigned region.
>>>
>>> Patch is a prerequisite to implement address translation which uses
>>> struct cxl_region to store all relevant region and interleaving
>>> parameters.
>>>
>>> Signed-off-by: Robert Richter <rrichter@....com>
>>
>> Just a nit below. Otherwise looks ok
>>
>> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
>>
>>> ---
>>>  drivers/cxl/core/region.c | 17 +++++++++++++++++
>>>  drivers/cxl/cxl.h         |  2 ++
>>>  2 files changed, 19 insertions(+)
>>>
>>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>>> index 2c37c060d983..777d04870180 100644
>>> --- a/drivers/cxl/core/region.c
>>> +++ b/drivers/cxl/core/region.c
>>> @@ -664,6 +664,11 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
>>>  		return PTR_ERR(res);
>>>  	}
>>>  
>>> +	cxlr->hpa_range = (struct range) {
>>> +		.start = res->start,
>>> +		.end = res->end,
>>> +	};
>>> +
>>>  	p->res = res;
>>>  	p->state = CXL_CONFIG_INTERLEAVE_ACTIVE;
>>>  
>>> @@ -700,8 +705,14 @@ static int free_hpa(struct cxl_region *cxlr)
>>>  	if (p->state >= CXL_CONFIG_ACTIVE)
>>>  		return -EBUSY;
>>>  
>>> +	cxlr->hpa_range = (struct range) {
>>> +		.start = 0,
>>> +		.end = -1,
>>> +	};
>>> +
>>>  	cxl_region_iomem_release(cxlr);
>>>  	p->state = CXL_CONFIG_IDLE;
>>> +
>>
>> stray blank line
>>>  	return 0;
>>>  }
> 
> This small cleanup was intended and separates the return from other
> statements to better group the code in (sort of) blocks. It is not
> worth separate patch and it is common practice to have small cleanups
> in the area of code that is changed. That allows small style fixes to
> the code while reworking it, but avoids separate code cleanups causing
> extra efforts, conflicts and the risk of changing stable code.
> 
> Anyway, let me know if you want me remove the change.

Yeah please just drop the change. While it's nice to have, it may potentially cause backport issues generally speaking. 

> 
> Thanks,
> 
> -Robert